U.S. patent application number 13/004630 was filed with the patent office on 2012-07-12 for vehicle engine sound enhancement.
Invention is credited to Cristian M. Hera, Dennis D. Klug.
Application Number | 20120177214 13/004630 |
Document ID | / |
Family ID | 45563526 |
Filed Date | 2012-07-12 |
United States Patent
Application |
20120177214 |
Kind Code |
A1 |
Hera; Cristian M. ; et
al. |
July 12, 2012 |
VEHICLE ENGINE SOUND ENHANCEMENT
Abstract
An engine harmonic enhancement system. The EHE system uses
multiple parameters, such as engine load, gear, number of cylinders
operating, and transmission ratio, to determine EHE gains to
determine EHE gain. The EHE system determines a separate EHE gain
for each harmonic.
Inventors: |
Hera; Cristian M.;
(Framingham, MA) ; Klug; Dennis D.; (West
Bloomfield, MI) |
Family ID: |
45563526 |
Appl. No.: |
13/004630 |
Filed: |
January 11, 2011 |
Current U.S.
Class: |
381/73.1 |
Current CPC
Class: |
G10K 15/02 20130101;
G10K 2210/3031 20130101; H04R 2430/01 20130101; H04R 1/028
20130101; B60Q 5/00 20130101; G10H 2250/371 20130101; G10K
2210/3016 20130101; A63H 17/34 20130101; H04R 2499/13 20130101;
G10K 2210/3046 20130101; G10K 2210/1282 20130101; H04R 1/22
20130101 |
Class at
Publication: |
381/73.1 |
International
Class: |
H04R 3/02 20060101
H04R003/02 |
Claims
1. A method, comprising: providing a fundamental frequency
corresponding to the RPM of an engine of a vehicle; determining a
plurality of harmonics of the fundamental frequency; and
determining an engine harmonic enhancement gain for at least one of
the plurality of harmonics that is different from the engine
harmonic enhancement gains corresponding to the other
harmonics.
2. The method of claim 1, wherein the determining an engine
harmonic enhancement gain comprises separately determining an
engine harmonic gain for each harmonic.
3. The method of claim 1, wherein the determining an engine
harmonic gain comprises determining the engine load.
4. The method of claim 3, wherein the determining the engine load
comprises one of determining the accelerator pedal position,
determining the mass air flow, determining the manifold absolute
pressure, or determining the engine torque.
5. The method of claim 1, wherein the determining of an engine
harmonic gain for the at least one of the plurality of harmonics
further comprises determining the value of a parameter other than
the engine load related to an operating condition of a vehicle; and
responsive to the value of the parameter and the engine load,
determining the engine harmonic enhancement gain.
6. The method of claim 1, wherein the circuitry for determining of
an engine harmonic gain for at least one of the plurality of
harmonics comprises determining the value of a first parameter
related to an operating condition of a vehicle; determining the
value of a second parameter, different from the first parameter,
related to an operating condition of the vehicle; and responsive to
the value of the first parameter and the second parameter,
determining the engine harmonic enhancement gain.
7. The method of claim 6, wherein the first parameter is the gear
in which the vehicle is operating.
8. The method of claim 6, wherein the first parameter is the number
of cylinders that are operating.
9. The method of claim 6, wherein the first parameter is the
transmission ratio of a continuously variable transmission.
10. The method of claim 1, wherein the determining comprises
selecting an engine enhancement gain from a look up table.
11. An engine harmonic enhancement system, comprising: circuitry
for providing a fundamental frequency corresponding to the RPM of
the engine; circuitry for determining a plurality of harmonics of
the fundamental frequency; and circuitry for determining an engine
harmonic enhancement gain for at least one of the plurality of
harmonics that is different from the engine harmonic enhancement
gains corresponding to the other harmonics.
12. The apparatus of claim 11, wherein the circuitry for
determining an engine harmonic enhancement gain comprises circuitry
for separately determining an engine harmonic gain for each
harmonic.
13. The apparatus of claim 11, wherein the circuitry for
determining an engine harmonic gain comprises circuitry for
determining the engine load.
14. The apparatus of claim 13, wherein the circuitry for
determining the engine load comprises one of circuitry for
determining the accelerator pedal position, circuitry for
determining the mass air flow, circuitry for determining the
manifold absolute pressure, or circuitry for determining the engine
torque.
15. The apparatus of claim 11, wherein the circuitry for
determining and engine harmonic gain further comprises circuitry
for determining the value of a parameter other than the engine load
related to an operating condition of a vehicle.
16. The apparatus of claim 11, wherein the circuitry for
determining of an engine harmonic gain for at least one of the
plurality of harmonics comprises circuitry for determining the
value of a first parameter related to an operating condition of a
vehicle; circuitry for determining the value of a second parameter
related to an operating condition of the vehicle, different from
the first parameter; and circuitry responsive to the value of the
first parameter and the second parameter, for determining an engine
harmonic enhancement gain.
17. The apparatus of claim 16, wherein the first parameter is the
gear in which the vehicle is operating.
18. The apparatus method of claim 16, wherein the first parameter
is the number of cylinders that are operating.
19. The apparatus method of claim 16, wherein the first parameter
is the transmission ratio of a continuously variable
transmission.
20. A method comprising: determining the value of a first parameter
related to an operating condition of a vehicle; determining the
value of a second parameter, different from the first parameter,
related to an operating condition of the vehicle; and responsive to
the value of the first parameter and the second parameter,
determining an engine harmonic enhancement gain.
21. The method of claim 20, wherein the determining the engine
harmonic enhancement gain comprises determining separately a gain
corresponding to each of the plurality of harmonics of the
fundamental engine frequency, wherein the engine harmonic gain
corresponding to at least one of the harmonics is different that
the engine harmonic gains corresponding to the other harmonics; and
further comprising applying to the fundamental engine frequency and
to each of the plurality of harmonics of the fundamental engine
frequency a corresponding engine harmonic enhancement gain.
22. The method of claim 20, wherein the first parameter is the gear
in which the vehicle is operating.
23. The method of claim 20, wherein the first parameter is the
number of cylinders that are operating.
24. The method of claim 20, wherein the first parameter is the
transmission ratio of a continuously variable transmission.
25. The method of claim 20, wherein the second parameter is the
engine load.
26. Apparatus comprising: circuitry for determining the value of a
first parameter related to an operating condition of a vehicle;
circuitry for determining the value of a second parameter related
to an operating condition of the vehicle, different from the first
parameter; and circuitry responsive to the value of the first
parameter and the second parameter, for determining an engine
harmonic enhancement gain.
27. The apparatus of claim 26, wherein the circuitry for
determining the engine harmonic enhancement gain comprises
circuitry for determining separately an engine harmonic gain
corresponding to each of the plurality of harmonics of the
fundamental engine frequency, wherein the engine harmonic gain
corresponding to at least one of the harmonics is different that
the engine harmonic gains corresponding to the other harmonics; and
further comprising circuitry for applying to the fundamental engine
frequency and to each of the plurality of harmonics of the
fundamental engine frequency a corresponding engine harmonic
enhancement gain.
28. The apparatus of claim 26, wherein the first parameter is the
gear in which the vehicle is operating.
29. The apparatus of claim 26, wherein the first parameter is the
number of cylinders that are operating.
30. The apparatus of claim 26, wherein the first parameter is the
transmission ratio of a continuously variable transmission.
31. The apparatus of claim 26, wherein the second parameter is the
engine load.
Description
BACKGROUND
[0001] This specification describes a vehicle engine sound
enhancement system. Engine sound enhancement systems provide
enhanced sound to modify the sonic and/or vibratory experience of a
vehicle driver or a vehicle occupant. In a hybrid vehicle, the
sound enhancement system may provide to the driver a constant sonic
experience, despite changes from internal combustion power to
electric motor power and to smooth the transition of the engine
sound during changes. An engine sound enhancement system may allow
the occupants to experience the engine sound at a loud,
stimulating, level, without being annoyingly loud to persons
outside the vehicle.
[0002] For further background, reference is made to U.S. patent
application Ser. No. 12/716,887.
SUMMARY
[0003] In one aspect of the specification, a method includes
providing a fundamental frequency corresponding to the RPM of an
engine of a vehicle, determining a plurality of harmonics of the
fundamental frequency, and determining an engine harmonic
enhancement gain for at least one of the plurality of harmonics
that is different from the engine harmonic enhancement gains
corresponding to the other harmonics. The determining an engine
harmonic enhancement gain may include separately determining an
engine harmonic gain for each harmonic. The determining an engine
harmonic gain may include determining the engine load. The
determining the engine load may include one of determining the
accelerator pedal position, determining the mass air flow,
determining the manifold absolute pressure, or determining the
engine torque. The determining of an engine harmonic gain for the
at least one of the plurality of harmonics further may include
determining the value of a parameter other than the engine load
related to an operating condition of a vehicle, and responsive to
the value of the parameter and the engine load, determining the
engine harmonic enhancement gain. The circuitry for determining of
an engine harmonic gain for at least one of the plurality of
harmonics may include determining the value of a first parameter
related to an operating condition of a vehicle, determining the
value of a second parameter, different from the first parameter,
related to an operating condition of the vehicle, and responsive to
the value of the first parameter and the second parameter,
determining the engine harmonic enhancement gain. The first
parameter may be the gear in which the vehicle is operating. The
first parameter may be the number of cylinders that are operating.
The first parameter may be the transmission ratio of a continuously
variable transmission. The determining may include selecting an
engine enhancement gain from a look up table.
[0004] In another aspect of the specification, an engine harmonic
enhancement system includes circuitry for providing a fundamental
frequency corresponding to the RPM of the engine, circuitry for
determining a plurality of harmonics of the fundamental frequency,
and circuitry for determining an engine harmonic enhancement gain
for at least one of the plurality of harmonics that is different
from the engine harmonic enhancement gains corresponding to the
other harmonics. The circuitry for determining an engine harmonic
enhancement gain may include circuitry for separately determining
an engine harmonic gain for each harmonic. The circuitry for
determining an engine harmonic gain may include circuitry for
determining the engine load. The circuitry for determining the
engine load may include one of circuitry for determining the
accelerator pedal position, circuitry for determining the mass air
flow, circuitry for determining the manifold absolute pressure, or
circuitry for determining the engine torque. The circuitry for
determining and engine harmonic gain further may include circuitry
for determining the value of a parameter other than the engine load
related to an operating condition of a vehicle. The circuitry for
determining of an engine harmonic gain for at least one of the
plurality of harmonics may include circuitry for determining the
value of a first parameter related to an operating condition of a
vehicle, circuitry for determining the value of a second parameter
related to an operating condition of the vehicle, different from
the first parameter, and circuitry responsive to the value of the
first parameter and the second parameter, for determining an engine
harmonic enhancement gain. The first parameter may be the gear in
which the vehicle is operating. The first parameter may be the
number of cylinders that are operating. The first parameter may be
the transmission ratio of a continuously variable transmission.
[0005] In another aspect of the specification, a method includes
determining the value of a first parameter related to an operating
condition of a vehicle, determining the value of a second
parameter, different from the first parameter, related to an
operating condition of the vehicle, and responsive to the value of
the first parameter and the second parameter, determining an engine
harmonic enhancement gain. The determining the engine harmonic
enhancement gain may include determining separately an engine
harmonic enhancement gain corresponding to each of the plurality of
harmonics of the fundamental engine frequency. The engine harmonic
gain corresponding to at least one of the harmonics may be
different that the engine harmonic gains corresponding to the other
harmonics. The method may further includes applying to the
fundamental engine frequency and to each of the plurality of
harmonics of the fundamental engine frequency a corresponding
engine harmonic enhancement gain. The first parameter may be the
gear in which the vehicle may be operating. The parameter may be
the number of cylinders that are operating. The parameter may be
the transmission ratio of a continuously variable transmission. The
second parameter may be the engine load.
[0006] In another aspect of the specification, an apparatus
includes circuitry for determining the value of a first parameter
related to an operating condition of a vehicle, circuitry for
determining the value of a second parameter related to an operating
condition of the vehicle, different from the first parameter, and
circuitry responsive to the value of the first parameter and the
second parameter, for determining an engine harmonic enhancement
gain. The circuitry for determining the engine harmonic enhancement
gain may include circuitry for determining separately an engine
harmonic gain corresponding to each of the plurality of harmonics
of the fundamental engine frequency. The engine harmonic gain
corresponding to at least one of the harmonics may be different
that the engine harmonic gains corresponding to the other
harmonics. The apparatus may further include circuitry for applying
to the fundamental engine frequency and to each of the plurality of
harmonics of the fundamental engine frequency a corresponding
engine harmonic enhancement gain. The apparatus of claim 4 first
parameter may be the gear in which the vehicle is operating. The
first parameter may be the number of cylinders that are operating.
The first parameter may be the transmission ratio of a continuously
variable transmission. The second parameter may be the engine
load.
[0007] Other features, objects, and advantages will become apparent
from the following detailed description, when read in connection
with the following drawing, in which:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0008] FIG. 1 is a block diagram of a vehicle including a vehicle
engine sound enhancement system;
[0009] FIG. 2 is block diagram of a front end of an engine harmonic
enhancement (EHE) processor;
[0010] FIGS. 3A-3C are block diagrams of back ends of an EHE
processor;
[0011] FIGS. 4A and 4B are block diagrams of a sound stage
processor and an amplifier
[0012] FIGS. 5A-5C are block diagrams showing EHE gain and delay
determiners and other elements of an EHE processor; and
[0013] FIGS. 6-10 are three dimensional plots of sound pressure
level (SPL), engine speed, and engine load.
DETAILED DESCRIPTION
[0014] Though the elements of several views of the drawing may be
shown and described as discrete elements in a block diagram and may
be referred to as "circuitry", unless otherwise indicated, the
elements may be implemented as one of, or a combination of, analog
circuitry, digital circuitry, or one or more microprocessors
executing software instructions. The software instructions may
include digital signal processing (DSP) instructions. Operations
may be performed by analog circuitry or by a microprocessor
executing software that performs the mathematical or logical
equivalent to the analog operation. Unless otherwise indicated,
signal lines may be implemented as discrete analog or digital
signal lines, as a single discrete digital signal line with
appropriate signal processing to process separate streams of audio
signals, or as elements of a wireless communication system. Some of
the processes may be described in block diagrams. The activities
that are performed in each block may be performed by one element or
by a plurality of elements, and may be separated in time. The
elements that perform the activities of a block may be physically
separated. One element may perform the activities of more than one
block. Unless otherwise indicated, audio signals or video signals
or both may be encoded and transmitted in either digital or analog
form; conventional digital-to-analog or analog-to-digital
converters may be omitted from the figures.
[0015] FIG. 1 is a block diagram of a vehicle including a vehicle
engine sound enhancement system. An engine harmonic enhancement
(EHE) processor 12 is coupled to a summer 14. The summer 14 may be
implemented as a plurality of summers, as will be shown in
subsequent figures. Also coupled to the summer 14 by an
entertainment audio equalizer and spatial processor 16 is an
entertainment audio signal source 18. The summer 14 is coupled
through a multi-channel amplifier 20 to a number of loudspeakers
22-1-22-4 positioned about the vehicle cabin, and in some
implementations may be positioned, for example as loudspeaker 24 to
radiate acoustic energy to the exterior of the vehicle. The
operational coupling between the engine harmonic audio signal
source and the EHE EQ and spatial processor is indicated by a
single line. The couplings between the EHE processor 12, the
entertainment audio equalizer and spatial processor 16, the summer
14, and the amplifier 20 may be multichannel, as indicated by the
multiple lines. As stated above, signal lines may be implemented as
discrete analog or digital signal lines, as a single discrete
digital signal line with appropriate signal processing to process
separate streams of audio signals, or as elements of a wireless
communication system.
[0016] In operation, the entertainment audio source 18 and
entertainment audio equalizer and spatial processor 16 operate
conventionally, to provide equalized and spatially processed audio
entertainment to the occupants of the vehicle cabin. In some
implementations, the entertainment audio signal source can include
announcement audio signals, for navigation, warning signals, and
the like. The EHE audio signal source provides signals representing
synthetically created or recorded engine sounds of harmonic
frequencies related to the engine speed, typically referenced in
revolutions per minute (RPM). The EHE processor 12 processes the
EHE audio signals so that, when reproduced by the loudspeakers
22-1-22-4 and 24 they provide a desired sonic experience. For
example, it may be desired for the sound corresponding to EHE audio
signals to appear to come from either a front engine bay 17 or a
rear exhaust pipe 19. The processed EHE audio signals and the
processed entertainment audio signals are summed at summer 14,
amplified by amplifier 20 and transduced to acoustic energy by the
loudspeakers 22-1-22-4 and 24.
[0017] FIG. 2 is block diagram of the front end 12F of an EHE
processor, in greater detail. An RPM detector and fundamental
frequency calculator 28 receives as input a signal indicative of
the engine speed in RPM. The RPM detector and fundamental frequency
calculator 28 is operationally coupled to an RPM rate of change
detector 30, an RPM in-range detector 32, and a harmonics generator
34. An engine load detector 36 receives as input a signal
indicative of engine load and is operationally coupled to an engine
load gain change detector 39. If it is desired for parameters other
than the engine load to affect the EHE gain, parameter detectors,
represented by elements 136 and 236 may receive a signal indicative
of the value of the parameter. Parameters will be discussed more
completely below.
[0018] In operation, the RPM signal that is input to the RPM
detector and fundamental frequency calculator 28 determines the
fundamental frequency of the engine harmonics and the engine load
signal controls the overall sound level of the harmonic
enhancement. "Harmonics" as used herein can include half harmonics
or quarter harmonics, and for simplicity includes the fundamental
frequency. The RPM signal can be an analog signal over a wire or a
digital signal over a bus (GMLAN, CAN, MOST, etc.). In one
implementation, the RPM signal indicates a known number of pulses
per engine revolution. If the RPM signal comes from an ignition
module, the number of pulses per revolution (PPR) is usually equal
to the number of engine cylinders which fire each revolution or
half of the total number of active engine cylinders since only half
of a conventional (four-stroke) engine's cylinders fire each
revolution. For example, an ignition-based RPM signal from an 8
cylinder engine will have 4 PPR. If the RPM comes from a crankshaft
sensor the number of pulses is equal to the number of
equally-spaced teeth on the crankshaft position wheel, not
including special teeth used to indicate crank position, typically
to indicate the top-dead-center (TDC) position of the
crankshaft.
[0019] The RPM detector and fundamental harmonic frequency
calculator 28 measures the time between successive RPM pulses, and
computes the reciprocal to determine the fundamental engine
harmonic frequency. To reject TDC pulses or errors in RPM
detection, the detector may replace a new pulse period with, for
example, a previous pulse period if the new pulse period is greater
than a predetermined tolerance (e.g. +/-25%) of the previously
accepted pulse period.
[0020] The engine load detector 36 determines the inherent engine
sound level to properly balance the sound enhancement. A signal
representing engine load is well suited for controlling sound
enhancement level for at least two reasons. First, overall engine
noise levels increase monotonically with increasing positive engine
loads. Second, strong enhancement is typically desirable only for
positive engine loads, when the engine propels the transmission.
Negative engine loads occur when the transmission propels the
engine, also known as engine brake. While there may be high levels
of inherent engine noise for during engine brake, noise
cancellation may be desired for this situation but significant
sound enhancement is rarely desired.
[0021] A vehicle's Engine Control Unit (ECU) will typically have
available several of the following signals which correlate well
with the engine load and may be available to the EHE system either
in analog or digital form, for example, accelerator pedal position
(APP); throttle position sensor (TPS); mass air flow (MAF);
manifold absolute pressure (MAP); engine torque; and/or computed
engine load. Any one of these signals is suitable for EHE control
if there is sufficiently-close-to one-to-one relationship between
that signal and the desired sound level of the harmonic
enhancement.
[0022] The engine load detector 36 may convert the engine load
signal from a native data form to a form more useful to the EHE
system. For example, if the engine load signal is representative of
the engine torque, the engine load detector may convert the torque
measurement to an engine load measurement. The engine load may be
expressed as an index; for example, the maximum engine load may be
designated as 100 and the engine load may be expressed as number
from 1-100. Likewise, the parameter detectors 126, 236 may convert
parameter value signals from a native form into a form more useful
by the EHE system.
[0023] The RPM rate of change detector 30 detects the rate of
change of the RPM. An engine should emit pleasant, audible,
powerful sounds as aural feedback only when a driver requires
significant amounts of power from it. Such usage is usually coupled
with both markedly increasing engine load and RPM. Under other
engine load conditions the engine should be quieter. When a vehicle
is cruising on a level highway both engine load and RPM are
generally steady. During vehicle deceleration at a fixed
transmission gear, both engine load and RPM drop. Therefore, the
RPM rate of change detector 30 may cause the EHE system to be
turned off, for example whenever the change in RPM is either small
or decreasing. There may be other situations in which the RPM rate
of change detector causes the EHE system to operate differently,
for example when a RPM rate of change associated with "double
clutching" is detected.
[0024] The RPM in-range detector 32 determines if the fundamental
engine rotation frequency is below a minimum frequency threshold or
above a maximum frequency threshold that determine a range of RPM
within which the EHE system is designed to operate.
[0025] The engine load gain change detector 39 determines whether
the engine load is increasing or decreasing and may determine the
rate at which the engine load is increasing or decreasing.
Generally, a more realistic effect is attained if the amplitude of
the EHE signal tracks the engine load if the engine load is
increasing, but decreases more gradually than the engine load if
the engine load is decreasing.
[0026] The harmonics generator 34 determines and outputs two
parameters for each enhanced engine harmonic (which could be a
non-integer harmonic). To determine a first parameter, the
harmonics generator 34 computes the frequency for each enhanced
harmonic by multiplying the fundamental engine rotation frequency
by the order of each enhanced engine harmonic and outputs a
sinusoid signal at the frequency. To determine a second parameter,
the harmonics generator converts the fundamental frequency into an
index to the harmonic shape, that is, it determines a sound
pressure level (SPL) for each harmonic as the SPL varies with RPM.
Typically, the harmonic shape is expressed as a Look-Up Table
(LUT). Alternatively, the harmonic shape may be calculated or
approximated according to a formula.
[0027] FIG. 3A is a block diagram of the back end 12B-1 of an EHE
processor. An EHE gain and delay determiner 21 is operationally
coupled to receive input from the RPM rate of change detector 30
(not shown in this figure), the engine load detector 36 and the RPM
in-range detector 32 (not shown in this figure) and to output a
signal to overall enhancement gain 50. Additionally, the EHE gain
and delay determiner 21 is operationally coupled to the parameter
signal sources here designated parameter 1 signal 126 . . .
parameter n signal 236. Overall enhancement gain 50 is coupled to
sound stage processor 52. H1 shape determiner 44-1 . . . Hn shape
determiner 44-n are operationally coupled to the harmonics
generator 34 of FIG. 2. Multipliers 46-1 . . . 46-n are
operationally coupled to corresponding harmonic shape determiners
44-1 . . . 44-n, to the harmonics generator 34 of the engine
harmonic audio signal source 10 of FIG. 2, and to a corresponding
harmonic gain 48-1 . . . 48-n. Harmonic gains 48-1 . . . 48-n are
operationally coupled to harmonics summer 42.
[0028] A "parameter," as used herein refers to a condition or
measurement which is desired to affect the gain or delay of the EHE
signal. Examples of parameters include the gear in which the
vehicle is operating; the transmission ratio or transmission ratio
interval of a continuously variable transmission (CVT); and an
"operational mode" of the engine. For example, if the engine is
capable of running on all cylinders or a subset of cylinders (such
as an 8 cylinder engine is designed to run on 8, 6, or 4
cylinders), the "operational mode" could refer to the number of
cylinders which are operating. Operational modes could also be used
to provide a different sonic experience for the same vehicles or
similar vehicles, depending on the wishes of the manufacturer or
user. For example, a vehicle may have a sports sedan model with a
sonic profile different from the profile of a touring sedan model.
Operational modes could also designate whether a hybrid car is
operating on electric or internal combustion power. For example,
the gear in which the vehicle is operating, the transmission ratio,
or the operational mode of the vehicle is typically available on
the bus mentioned below in the discussion of the RPM signal. If the
vehicle does not have a bus, the parameter detector may derive the
information from available information; for example, the gear in
which the vehicle is operating may be inferred from the vehicle
velocity and the RPM.
[0029] The harmonic shape determiners 44-1-44-n of FIG. 3A are
typically implemented as frequency-to-gain look-up tables (LUTs)
which enables the sound level of each enhanced harmonic to be
frequency dependent. Alternatively, the harmonic shape may be
calculated or approximated according to a formula. This shape
control outputs a gain which adjusts the harmonic enhancement
level. The resulting enhancement, output through the speakers and
acoustically summed with the inherent harmonic sound level,
produces a sound level which matches a desired target. The gain for
each harmonic can be zero (indicating that there is no enhancement
at that harmonic) or unity. To achieve this goal, the look-up table
must account for the inherent harmonic level, the target harmonic
level, and the transfer function of the audio system, all ideally
measured at the occupant's ears. The look-up tables should have
enough frequency resolution such that sound level values
interpolated between adjacent frequency indices satisfy desired
enhancement requirements and not cause enhancement artifacts due to
too-coarse frequency spacing. For computational efficiency all the
harmonic shape LUT's may use the same frequency indices, usually
based on the first harmonic of the engine RPM. If so, then all
shape LUT's will have the same number of entries. Assuming this is
the case, the highest order EHE harmonic will dictate the required
number of LUT entries because it will cover the greatest range of
frequencies for a given RPM range. For example, a first order
harmonic will cover a 90 Hz range (10 to 100) for a RPM range from
600 to 6000, while a tenth order harmonic will cover 900 Hz for the
same RPM range.
[0030] The harmonic gains 48-1 . . . 48-n apply individual harmonic
specific gains to each of the harmonics, based on input from the
harmonic shape LUT's 44-1-44-n and the instantaneous values of the
sinusoids for each of the harmonic frequencies determined by the
harmonics generator 34.
[0031] The EHE gain and delay determiner 21 determines the amount
of gain and delay to be applied by the EHE overall enhancement gain
50. The EHE gain and delay determiner may apply a gain function
(also referred to as a "mapping function" or "mapping") which
includes as variables the engine load, the change in engine load,
the RPM, and the rate of change in RPM to determine the EHE gain
(as described in U.S. patent application Ser. No. 12/716,887).
Additionally, the gain function applied by the EHE gain and delay
determiner 21 may use as variables values of other parameter which
are received from sources such as parameter 1 detector 136 . . .
parameter m detector 236. The EHE gain and delay determiner 21 may
smooth the gain values so that the sound variation is natural, and
undistorted, similar to the sound variation in time of a mechanical
system.
[0032] The overall enhancement gain 50 can change the overall sound
level of individual harmonics without changing the
frequency-dependent "shape" of the enhancement.
[0033] The sound stage processor 52 processes the summed-and-scaled
EHE signal to provide the acoustic imaging of the sound enhancement
system. The sound stage processor processes the EHE signal through
a separate audio equalization filter for each loudspeaker 22-1-22-4
and 24 of FIG. 1. The EHE signal can be monophonic, indicating that
the same signal is provided to all loudspeakers 22-1-22-4, or may
be multichannel, for example sterophonic. In one implementation,
the outputs to one or more of loudspeakers 22-1-22-4 are phase
shifted relative to the other outputs to the other loudspeakers.
The audio equalization filters control the magnitude and phase
response as a function of frequency, and delays. Besides the
conventional entertainment audio equalization and spatial imaging
tuning techniques, sound stage processor 52 may also adjust the
gain and even turn off certain EHE speakers over certain frequency
ranges to achieve the desired sonic imaging. Because EHE imaging
requirements are usually different from the requirements for
entertainment audio at least some of the EHE equalization
components may be separate from the entertainment audio
equalization. The sound stage processor 52 operates on the EHE
signal to achieve not only the desired amplitudes of the desired
harmonics, but also to achieve the desired apparent source of the
engine harmonics, for example the engine bay 17 or the muffler 19
of FIG. 1.
[0034] An EHE EQ and spatial processor according to FIG. 3A permits
a number of parameters, in addition to engine load, to affect the
EHE enhancement signal. Permitting parameters in addition to the
engine load provides a more realistic sonic experience.
[0035] The back end 12B-2 of the EHE processor of FIG. 3B does not
have the harmonics summer 42, the overall enhancement gain 50 or
the EHE gain and delay determiner 21 of FIG. 3A. Instead, the back
end 12B-2 of the EHE processor of FIG. 3B has separate gains
50-1-50-n, and separate EHE gain and delay determiners 21-1-21-n,
one for each harmonic. The gain for each harmonic can be zero
(indicating that there is no enhancement at that harmonic) or
unity. The individual gain and delay determiners may determine or
approximate the EHE gain by calculation or may retrieve the EHE
gain from a lookup table. Data from the engine load gain determiner
can be used to provide a different harmonic shape depending on the
engine load.
[0036] In operation, each EHE gain and delay determiner 21-1-21-n
receives input from the engine load detector 36. Based on the input
from the engine load detector 36, each EHE gain and delay
determiner 21-1-21-n determines a gain to be applied by
corresponding gain 50-1-50-n. Additionally, the EHE gain
determiners 21-1-21-n may use the change in engine load, the RPM,
and the rate of change in RPM to determine the EHE gain (similar to
the manner described in U.S. patent application Ser. No.
12/716,887).
[0037] The back end 12B-2 of the EHE processor of FIG. 3B permits
the EHE system to allow the engine load to affect the individual
harmonics differently, thereby permitting finer control of the EHE
signal.
[0038] The back end 12B-3 of the EHE processor of FIG. 3C has
elements of both EHE processor back ends 12B-1 and 12B-2 of FIGS.
3A and 3B, respectively, including separate gains 50-1-50-n, and
separate EHE gain and delay determiners 21-1-21-n, one for each
harmonic, similar to FIG. 3B. Each of the EHE gain and delay
determiners 21-1 . . . 21-n receives inputs from the engine load
detector 36, and also the parameter gain determiners such as
parameter 1 detector 136 . . . parameter m detector 236. The
individual gains gain and delay determiners may determine the EHE
gain by calculation or may retrieve the EHE gain from a lookup
table. The gain for each harmonic can be zero (indicating that
there is no enhancement at that harmonic) or unity.
[0039] The back end 12B-3 of the EHE processor of FIG. 3C permits
multiple parameters to affect the EHE gain, and permits each of the
multiple parameters to affect each harmonic differently.
[0040] A sound stage processor 52 and the amplifier 20 are shown in
more detail in FIG. 4A. The sound stage processor 52 includes a
plurality of equalizers (EQs) 53-1-53-5, one for each speaker. The
amplifier 20 includes a plurality of summers 54-1-54-5 and a
plurality of channel amplifiers 56-1-56-5 both one for each
speaker. In some examples the number of equalizers may be greater
or less than the actual number of speakers, and equalize the signal
according to a set of ideal speaker locations. The equalized
outputs are re-mixed to match the actual number of speakers, either
by an additional stage of the sound stage processor 52 or by
processing within the amplifier 20.
[0041] In operation, each of the speaker EQs 53-1-53-5 applies an
equalization, which can include amplitude (which can include
turning off the speaker) and phase adjustment and application of
delay to the signal from the overall enhancement gain 50. The
individually equalized signals from the speaker EQs 53-1-53-5 are
summed in the amplifier at the summers 54-1-54-5 with the signals
from the entertainment audio system intended for the corresponding
speaker, and the summed signals are amplified by the channel
amplifiers 56-1-56-5. The amplified channels signals are then
transmitted to the loudspeakers 22-1-22-4 and 24, which transduce
the audio signals to sound.
[0042] FIG. 4B shows a sound stage processor 52 for use in the back
end 12B-2 and 12B-3 of FIG. 3B and FIG. 3C, respectively. The sound
stage processor 52 of FIG. 4B processes the summed-and-scaled EHE
signals from overall enhancement gains 50A-50n to determine an
acoustic imaging for each of the harmonics. The sound stage
processor separately processes each of the EHE signals from overall
enhancement gains 50A-50n through separate audio equalization
filters 53-1-53-5 for each loudspeaker 22-1-22-4 and 24 of FIG. 1.
Each equalization filter 53-1-53-5 may apply a different
equalization to the EHE signals from the overall enhancement gains
50A-50n, as represented by the separate paths in dashed lines
through the equalization filters 53-1-53-5. The equalization paths
are summed after equalization and provided to the amplifier 20. The
audio equalization filters control the magnitude and phase response
as a function of frequency, and delays. Besides the traditional
entertainment audio equalization and spatial imaging tuning
techniques, sound stage processor 52 may also adjust the gain and
even turn off certain EHE speakers over certain frequency ranges to
achieve the desired sonic imaging. Because EHE imaging requirements
are usually different from that for entertainment audio at least
some of the EHE equalization components may be separate from the
entertainment audio equalization. The sound stage processor 52
operates on the EHE signal to achieve not only the desired
amplitudes of the desired harmonics, but also to achieve the
desired apparent source for each of the sets of engine harmonics.
For example, the source of the higher end harmonics could be the
engine bay 17 and the source of the lower order harmonics could be
the muffler 19 of FIG. 1.
[0043] FIG. 5A shows an implementation of some elements of the back
end 12B-1 of EHE processor of FIG. 3A. In the implementation of
FIGS. 3A and 5A, multiple parameters are used to determine one
harmonic gain that is applied to all harmonics. The EHE gain and
delay determiner 21 includes an LUT 70 which maps parameters (in
this example engine load and gear) to gain. In this example, the
LUT has four entries (2 load values.times.2 gear values). The EHE
gain and delay determiner 21 also includes logic represented by a
first switch 210 that is responsive to input from the engine load
detector 36 of FIG. 2. The two output switch terminals of switch
210 are coupled to the input of switches 212A and 212B, which are
responsive to input from the parameter 1 detector 136 for FIG. 2;
in this implementation, parameter 1 is the gear in which the
vehicle is currently operating. Inputs to H1 shape determiners 44-1
. . . 44-n are not shown in this view.
[0044] In this implementation, if switch 210 is in the "0"
position, and switches 212A and 212B are in the "0" position,
switch 210 outputs a gain appropriate for the engine load
represented by load value 1 and for gear 1. Similarly, if switch
210 is in the "0" position, and switches 212A and 212B are in the
"1" position, switch 210 outputs a gain appropriate for the engine
load represented by load value 1 and for gear 2; if switch 210 is
in the "1" position, and switches 212A and 212B are in the "0"
position, switch 210 outputs a gain appropriate for the engine load
represented by load value 2 and for gear 1; and if switch 210 is in
the "1" position, and switches 212A and 212B are in the "1"
position, the EHE gain and delay determiner outputs a gain and
delay appropriate for the engine load represented by load value 2
and for gear 2. The process of determining an EHE gain is repeated
at intervals, for example 20 ms.
[0045] The gain that is output by switch 210 is provided to the
overall EHE gain element 50 through gain modification logic 60,
attack/decay logic 66, and gain smoother 62. The EHE gain element
50 applies the gain and delay to the summed harmonics. The
application of the gain and delay to the harmonics is repeated at
intervals, for example of about 90 .mu.s.
[0046] The gain modification logic 60 may modify the gain values
based on input from RPM rate of change detector 30, RPM in-range
detector 32, and engine load gain change detector 39. For example,
if one or more of the RPM, the RPM rate of change, or the engine
load change are out of the intended range of operation, the gain
modification logic may set the gain to zero, effectively turning
off the EHE system, may set the gain to 1 so the no gain is applied
to the by EHE gain element 50, or may set the gain to some minimum
or maximum value.
[0047] The attack/decay logic 66 may modify the gain, for example
by applying a delay, to be applied by the EHE system based on input
from the engine load gain change detector 39. As stated above in
the discussion of engine load gain change detector 39, a more
realistic effect is attained if the amplitude of the EHE signal
tracks the engine load if the engine load is increasing, but
decreases more gradually than the engine load if the engine load is
decreasing. If the engine load is decreasing, the attack/decay
logic 66 may apply a delay to the application of the gain.
[0048] The gain smoother 62 may smooth the stream of EHE gains to
reduce the possibility of abrupt changes in the EHE gain. The
smoothing may take the form of slewing, windowed averaging, low
pass filtering, a non-linear smoothing technique, a time-varying
smoothing technique, or others. In one implementation, the gain
smoother 62 is a low pass filter, which can be a single pole low
pass filter or a variable pole low pass filter. If the engine load
is decreasing, the gain smoother may change a smoothing parameter.
For example, the break frequency of a low pass filter may be
changed or the width of the window in a windowed averaging system
may be changed.
[0049] For simplicity of explanation and of the figures, the
implementation of FIG. 5A is shown with two gears and two load
values. In an actual implementation, a typical number of gears
would be four to six (and possibly more if a reverse gear is
included), and loads may be expressed as a percentage of maximum
load in one percent intervals, for example 1%, 2% . . . 99%, 100%
so there may be approximately 100 load values. Switches 210, 212A,
and 212B are for explanation only, and do not indicate that the
determination of the overall EHE gain must be done by switches. In
an actual implementation, the determination of the overall EHE gain
and delay may be done by a microprocessor selecting a value from a
cell of an LUT, or, less commonly, by calculation of a formula
relating the inputs to the EHE gain and delay determiner 21 with
the overall EHE gain. Furthermore, the block diagrams of the
figures show logical results, not necessarily the order in which
operations are performed, or how the operations are performed. For
example, "turning off" the EHE system could be done at gain
modification logic 60 by setting the EHE gain to zero, or could be
done by causing a microprocessor executing the operations of EHE
gain and delay determiner 21 to temporarily stop selecting EHE
gains from an LUT or by setting the EHE gain to zero.
[0050] FIG. 5B shows an implementation of some elements of the back
end 12B-2 of the EHE processor of FIG. 3B. Inputs to H1 shape
determiners 44-1 . . . 44-n are not shown in this view nor are
inputs to gain modification logic 60, attack/decay logic 66, and
gain smoother 62.
[0051] In the implementation of FIGS. 3B and 5B, a single parameter
is used to determine an enhancement gain for each harmonic. Each
EHE gain and delay determiner 21-1-21-n includes an LUT 72-1-72,
each LUT including two entries, one for each load value. Each EHE
gain and delay determiner 21-1-21-n also includes logic represented
by a switch 214, responsive to input from the engine load detector
36 of FIG. 2. If the switch 214 of gain and delay determiner 21-1
is in the "0" position, the EHE gain and delay determiner 212
outputs an EHE gain and delay appropriate for load value 1. If the
switch 214 is in the "1" position, the EHE gain and delay
determiner 212 outputs an EHE gain and delay appropriate for load
value 2. The gain and delay selected by the EHE gain and delay
determiner is provided to the overall EHE gain element 50-1 for
harmonic H1, which applies the gain and delay to harmonic H1. The
remaining EHE gain and delay determiners operate in a similar
manner. The EHE gain and delay for load 1 for harmonic H1 may be
the same or different than the EHE gain and delay for load 1 for
harmonic H2.
[0052] For simplicity of explanation and of the figures, the
implementation of FIG. 5B is shown with two load values. In an
actual implementation, there may be 99 or 100 load values. The use
of switch 214 is for explanation only, and does not indicate that
the determination of the overall EHE gain is done by switches. In
an actual implementation, the determination of the overall EHE gain
and delay may be done by a microprocessor selecting a value from a
cell an LUT for each harmonic, or, less commonly, by calculation of
a formula relating the input to the EHE gain and delay determiners
21-1-21-n with the overall EHE gain for each harmonic. A typical
number of harmonics for which EHE gain and delays are provided may
be six, or up to twelve to eighteen if there is more than one
engine mode.
[0053] Gain modification logic 60, attack/decay logic 66, and gain
smoother 62 operate on the steams of gains for each harmonic in the
manner described above in the discussion of FIG. 5A.
[0054] FIG. 5C shows an implementation of some elements of the back
end 12B-3 of the EHE processor of FIG. 3C. In the implementation of
FIGS. 3C and 5C, multiple parameters are used to determine an
enhancement gain for each of the harmonics. Inputs to H1 shape
determiners 44-1-44-n and to multipliers 46-1-46-n are not shown in
this view.
[0055] Each of the EHE gain and delay determiners 21-1-21-n
includes an LUT (74-1-74-n). Each LUT includes four entries (2 load
values.times.2 gear values). Each of the EHE gain and delay
determiners 21-1-21-n also includes logic represented by a first
switch 210 that is responsive to input from the engine load
detector 36 of FIG. 2. The two output switch terminals of switch
210 are coupled to the input of switches 212A and 212B, which are
responsive to input from the parameter 1 detector 136 for FIG. 2;
in this implementation, parameter 1 is the mode in which the
vehicle is currently operating. (As described above, in this
specification, "mode" may be a parameter of an engine that is
capable of running on all cylinders or a subset of cylinders. For
example, an 8 cylinder engine designed to run on 8, 6, or 4
cylinders has three modes: an 8 cylinder mode, a 6 cylinder mode,
and a 4 cylinder mode. Examples of other modes are described
above). The implementation of FIG. 5C has two modes. In the
implementation of FIG. 5C, if switch 210 is in the "0" position,
and switches 212A and 212B are in the "0" position, the EHE gain
and delay determiner outputs a gain and delay appropriate for the
engine load represented by load value 1 and for mode 1. Similarly,
if switch 210 is in the "0" position, and switches 212A and 212B
are in the "1" position, the EHE gain and delay determiner outputs
a gain and delay appropriate for the engine load represented by
load value 1 and for mode 2; if switch 210 is in the "1" position,
and switches 212A and 212B are in the "0" position, the EHE gain
and delay determiner outputs a gain and delay appropriate for the
engine load represented by load value 2 and for mode 1; and if
switch 210 is in the "1" position, and switches 212A and 212B are
in the "1" position, the EHE gain and delay determiner outputs a
gain and delay appropriate for the engine load represented by load
value 2 and for mode 2. The gain and delay selected by the EHE gain
and delay determiner is provided to the overall EHE gain element
50-1-50-n, which applies the gain and delay to corresponding
harmonic H1-Hn.
[0056] For simplicity of explanation and of the figures, the
implementation of FIG. 5C is shown with two modes and two load
values. In an actual implementation, a typical number of modes for
an LUT could be two or three and a typical number of load values
for the LUT could be 99 or 100. Switches 210, 212A, and 212B are
for explanation only, and do not indicate that the determination of
the overall EHE gain is done by switches. In an actual
implementation, the determination of the overall EHE gain and delay
may be done by a microprocessor selecting a value from a cell of an
LUT for each harmonic, or, less commonly, by calculation of a
formula relating the inputs to the EHE gain and delay determiner 21
with the overall EHE gain for each harmonic.
[0057] Gain modification logic 60, attack/decay logic 66, and gain
smoother 62 operate on the steams of gains for each harmonic in the
manner described above in the discussion of FIG. 5A.
[0058] FIGS. 6-10 are three dimensional plots with the SPL on the
vertical axis and the engine load and the RPM on the horizontal
axes.
[0059] FIG. 6 shows the behavior of an EHE system in which a single
parameter (typically, as in this example, engine load) determines
the EHE gain, and the same gain function is applied to all
frequencies and therefore to all harmonics. Curve 102 is a shows
how SPL varies with RPM at 100% load (sometimes referred as wide
open throttle [WOT] load). Curve 104 represents the gain function
that is applied across all frequencies. The application of the gain
function represented by curve 104 to curve 102 results in an
enhancement surface 103 shown in FIG. 7. The surface 103 can be
represented as a plurality of points, each having an RPM value, a
load value, and a corresponding SPL. The points correspond to
entries in an LUT. The surface 103 can also be represented as a
mathematical function with two independent variables (RPM and load
value), from which the SPL can be calculated or approximated.
[0060] FIG. 8 shows the behavior of an EHE system in which a single
parameter (typically, as in this example engine load) determines
the EHE gain, but different gain function are applied at some
frequencies or frequency bands.
[0061] In FIG. 8, there are five different gain functions
104-1A-104-5A. In this example, gain functions 104-1A, 104-2A,
104-4A, and 104-5A are identical, but gain function 104-3A, for the
RPM range from 3500 RPM to 4500 RPM, is different than gain
functions 104-1A, 104-2A, 104-4A, and 104-5A. Applying the gain
functions 104-1A-104-5A to the WOT curve 102 results in an
enhancement surface 106 of FIG. 9. An example of an EHE system that
has the behavior of FIGS. 8 and 9 is an EHE processor 12 with a
back end 12B-2 of FIG. 3B. The value of n in FIG. 3B would be five;
and EHE gain and delay determiners 21-1-21-5 corresponding to
harmonics in the range of 3500 RPM to 4500 RPM would apply the gain
function represented by curve 104-3A of FIG. 8 to determine the EHE
gain to apply to the harmonic. EHE gain and delay determiners
21-1-21-5 corresponding to harmonics not in the range of 3500 RPM
to 4500 RPM would apply the gain function represented by curves
104-1A, 104-2A, 104-4A, and 104-5A of FIG. 8 to determine the EHE
gain to apply to the harmonic.
[0062] FIG. 10 shows the behavior of an EHE in which multiple
parameters (in this example, engine load and gear) determine the
EHE gain, and a single gain function is applied to all frequencies.
In the example of FIG. 10, there are five gain functions or
mappings 104-1B-104-5B, one for each gear. Applying gain functions
104-1B-104-5B to WOT curve 102 would result in five enhancement
surfaces (not shown in this figure), one for each gear. An example
of an EHE system that has the behavior of FIG. 10 is an EHE system
with an EHE processor with a back end 12B-1 of FIG. 3A. The value
of n in FIG. 3A would be five; the value of m in FIG. 2 would be
two, and the two parameters would be engine load and gear. The
value of the gear parameter would determine which of the five
surfaces correspond to the gain function to be applied to the
harmonics.
[0063] Numerous uses of and departures from the specific apparatus
and techniques disclosed herein may be made without departing from
the inventive concepts. Consequently, the invention is to be
construed as embracing each and every novel feature and novel
combination of features disclosed herein and limited only by the
spirit and scope of the appended claims.
* * * * *